Como posso provar ao escritório da S.S que retornei a tempo sem o carimbo da alfândega dos EUA no meu passaporte? [fechadas]

Uma das opções seria manter os cartões de embarque. Se você usar o Global Entry, faça uma foto do recibo que sai da máquina antes de entregá-lo à alfândega.

De acordo com o link fornecido por Dennis em uma comment, os seguintes são obrigatórios como prova:

Obtain the following information when continuous presence must be proven:

1. Individual's statement

A signed statement from the claimant giving the date he/she entered the U.S., the place at which he/she stayed in this country during the first full month, and affirming that he/she did not go outside the U.S. at any time during such a month; and

2. Supporting evidence

Any evidence which establishes the claimant's date of entry into the U.S.; such as:

a. A copy of the return plane ticket, a passport showing the date of entry and date of departure, or similar evidence which establishes the date of entry; or

b. A signed statement from one or more U.S. residents having knowledge of the claimant's presence in the U.S. to corroborate his/her presence during the 30 days in question. A statement from the person who furnished the recipient lodging throughout the month in question is preferable. Statements from a member of the clergy, neighbors, or anyone else likely to have knowledge of the claimant's presence in this country are also acceptable. Persons executing corroborative statements must give their addresses and must indicate the basis for their knowledge.

NOTE: The date of departure is material for redeterminations to determine the duration of an absence. Use the evidence above to obtain such date.

Você também pode tentar mostrar cartões de crédito, cartões bancários ou outros recibos para transações nos EUA após a sua chegada.